For 26 years, doctors could not piece together the medical puzzle of Stewart Altman's symptoms -- as a child growing up on Long Island, he was uncoordinated and slurred his speech. Later, as a volunteer fireman, he kept falling down and had trouble climbing the ladders.

It seemed unrelated at the time, but his older sister, who had a history of psychological symptoms, was hospitalized in a mental institution. Her psychiatrist suspected a physical disorder and consulted a geneticist who eventually connected the dots.

In 1978, Altman and his sister Roslyn Vaccaro were given a stunning diagnosis: Tay-Sachs -- an inherited neurological disease that typically affects babies, killing them between the ages of 3 and 5. Only several hundred cases exist in the United States.

Altman, now 58, has a non-fatal, adult form of the disease, late onset Tay-Sachs (LOTS), and depends on his wife and a service dog to perform most daily tasks.

"I am devastated," Altman said of the disease that has robbed him of much of his speech and muscle strength, confining him to a wheelchair. "But the alternative is much worse."

His sister died in 2000 after battling LOTS-related bipolar disorder and schizophrenia -- which occurs in 50 to 60 percent of all adult cases -- and Altman and his wife raised her two sons.

Now scientists are hopeful that gene therapy may help late-onset patients like Altman and look forward to human trials.

Tay-Sachs is caused by gene mutation results in the absence or insufficient levels of the enzyme, hexosamindase A or Hex A. Without it, a fatty substance or lipids accumulates in the cells, mostly in the brain. It comes in three forms: infantile, juvenile or adult onset.

Doctors say there can be great variations in the presentation of Tay-Sachs, even in the same family with the same mutations. Babies born with Tay-Sachs appear normal at first, but by 3 or 4 years old, their nerve cells deteriorate and they eventually die. Those with LOTS can live a long life, but, like Altman, are progressively disabled.

The story of Tay-Sachs is a miraculous one. It was first identified in the late 1800s by British ophthalmologist Warren Tay and New York neurologist Bernard Sachs, who noticed the disease was prevalent in Jews of Eastern European origin.

In the 1970s and 1980s, when genetic testing became available, synagogues launched public education campaigns encouraging prospective parents to be tested, and the disease was virtually eliminated in those of Jewish ancestry.

Altman's speech is difficult to understand, so his wife Lorrie said her husband of 37 years wanted the public to know, "it's not just an infant's disease."

"Tay-Sachs is also in the general population and people don't know," she said. "He thinks we need to get the word out. One in 250 Americans carries the gene."

French Canadians, Louisiana Cajuns and even those of English-Irish ancestry have a greater chance of carrying the recessive gene that causes the disease.

Tay-Sachs is an autosomal recessive disorder, which means each parent must carry the gene. Their children have a 25 percent chance of developing Tay-Sachs, 50 percent chance of being a carrier and a 25 percent chance of being free of that recessive gene.

Altman was born in 1952, before genetic testing was available. Both his parents were carriers of the recessive gene that causes Tay-Sachs and both he and sister were stricken with the mildest form of the disease. Two of their brothers were unaffected, although one is a carrier.